Apparatus for automatically controlling the steam generation in highpressure steam plants



Nov. 17, 1931. w. STENDER 1,832,150

APPARATUS FOR AUTOMATICALLY CONTROLLING THE STEAM GENERATION INHIGH-PRESSURE STEAM PLANTS Filed-May 12, 1925 Fl/FL SUPPLY WITN E55INVENTOR M44 00mm? STE/V051? atented Nov. I 17, 1931 TED STATS TENTOFFICE MENS-SCHUCKERTWERKE GESELLSCHAFT MIT BESCHRKNKTER HAFTUNG, 0FSIE- MENSSTADT, NEAR BERLIN, GERMANY, A. CORPORATION OF GERMANYAPPARATUS FORA'UTOMATICALLY CONTROLLING THE STEAM GENERATION IN HIGH-PRESSURE STEAMPLANTS Application filed May 12, 1925, Serial No. 29,745,and in Germany May 18, 1924.

The invention relates'to improvements in an apparatus for automaticallycontrolling the steam generation in high-pressure steam plants in whichthe steam is generated near the critical pressure in a steam generatorwithout relatively large water and steam space in such a manner that thewater passes steadily from the liquid state into vapor .without adistinct separation. The steam is then throttled to a lower pressure foruse and during or after the throttling is superheated in order toprevent also subsequent condensation and thus a separation of water andsteam.

The subject matter of the present invention relates to particulararrangements in steam plants of the character referred to by which thepressure and the temperature of the working medium are simultaneouslyregulated in dependence of the varying power consumption of the plant byat least two independent fluctuation-responsive elements such that inthe steam generator the pressure always remains about at the criticalpressure and that in all stages of the steam generation the temperatureremains at such value that at no point of the system an irregularseparation between vapor and liquid occurs, such as would be the case inordinary low pressure steam boilers.

In the usual steam power plants with steam boiler the steam boileritself forms a large storage chamber, heat accumulator or reservoirwhich acts to a large extent as balancer or equalizer when the steamconsumption fluctuates owing to the stopping or the addition of engines,but which at least balances the pressure fluctuations until the furnacehas been adjusted. in correspondence with the fresh steam demand. Inplants of'the kind illustrated such a relatively large boiler whichcould serve as storage chamber or J reservoir does not exist, the boilerportion, if one may so term it, consisting merely of a tube system intowhich water is forced at near critical pressure, and which in a certainzone is heated above critical temperature. Such a system of course hasonly a small volume capacity and is not at all capable of exerting anybalancing efiect. In such steam an increased steam consumption wouldresuit in a very rapid decrease in pressure in the steam generator, allthe more since, as previously stated, the steam generator has noappreciable volume capacity. If now as would be done in ordinary lowpressure generatingv plants, only the feed-pump is automaticallyregulated in accordance with the increase in steam consumption theresult to be sure would be a restoration of the original pressure in theplant by mere increase in the quantity of feedwater. However, at thesame time the temperature would drop since the furnace, or'generallyspeaking the heat supplied, was also atthat time adjusted for the watervolume originally supplied by the feed-pump. Thus in the type ofgenerating plant with which the present invention deals it is notsuflicient to adjust the feed-pump alone to the new conditions, but itis also necessary to adjust the heat supply.

7 According to this invention the problem is solved by utilizing thepressure and temperature fluctuations which take place in the steamsupply pipe to the consumer when the running conditions change tocontrol the apparatus supplying the working materials, heat and waterviz. the furnace and the feed pump in such a manner that these elementsautomatically adapt themselves in their operation to the varying steamdemand. F or this purpose at various places of the plant, particu-.

larly in the steam consumption pipe itself elements are placed which areaffected by the temperatures or the pressure in the pipe line and whichtransmit this efiect to another point of the steam generating plantthrough the agency of suitable transmission means and there control athrottle valve or equivalent means and also control the output of thefeed pump and the furnace and so on. The mantail features and exchangesof the control means may be made within the scope of this disclosure,all with the same result, namely, to maintain the operating conditionsof such a plant on the basis of the principal requirements outlinedhereinbefore. In other words,

it should always be borne in mind that by at least two elements, eachresponsive to a different condition of the generator such as forinstance pressure and temperature the conditions must be supervised suchthat each particular condition is thereby maintained at its criticalvalue and that the temperature of the operating fluid in the successivestages of the steam generation to the point of delivery into the serviceline is maintained above the saturation temperature.

Referring to the drawing, for example the housing of a vertical steamgenerator, in which two pipe coils 2 and 4 are disposed. Coil 2 servesfor transforming the operating fluid from the li uid into the vaporousstate and in coil 4 t e vaporous operating fluid is superheated beforeit is delivered to the consumer. Their actual form, mechanicallyspeaking, is immaterial so far as the present inventlon is concerned.The pipe coils may be arranged in any suitable manner in the boilerhousing as may be known in the-art} and the superheater coils may bearranged in any manner relatively to the steam generating coils so thatthe desired result is attained.

The li uid operating fluid, for instance water, is rawn in by pump 1 anddelivered into the steam generator coil 2 at at least critical pressure.The pump may be operated by any suitable auxiliary power, for instanceby the turbine 21.. After the operating fluid has been transformed intosteam in coil system 2, the steam pressure is throttled down to thepressure required in the service pipe 5, by means of the throttle 3whence it passes into the coil system 4 where it is superheated. Thenceit passes into service ipe 5 which may forexample supply the turbine 6which operates electric generator 7. The exhaust steam from the turbine6 may be led for instance to the condenser 8 from which the condensateis again drawn in by pump 1.

In the present case for simplicity it is assumed that heat is suppliedto the steam generator thru an .oil burner which is indicated by thenozzle '10. Those skilled will understand that any other fuel such asas, coal dust or solid coal may be employe as 2a represents a fuelinstead, automatic supply controls equivalent to the liquid control mehere de scribed being per se known for all sorts of fuels.

In the present case the burner 10 is supplied with liquid fuel by meansof a pump 20 which is actuated by an auxiliary power unit 19.

According to this invention an element 11 sensitive to pressure (such asany well known diaphragm servo-motor) is, for instance, connectedbetween the super-heater 4 and the steam consumer 6 through the pressuretransmitting means 12 so that the steam pressure variations aretransmitted to the throttling device 3 in such a sense that when thepressure in the pipe 5 decreases the throttle 3 is further opened andwhen it rises this throttle is further closed. The throttle 3 issituated between the steam generator 2 and the superheater 4 and thuscontrols the amount of steam entering the superheater. According to thisinvention the feed pump 1 may be controlled thru line 14 by means of adiaphragm servo-motor 13 sensitive to varying pressure existing in thesteam generator and actuating by its response throttle valve 13, whichcontrols the pump output, in such a. manner that the feed pump 1replaces the weight of steam-given off by the generator and thus keepsthe pressure in the generator 2 constant. The furnace or the burner 10can according to this invention be affected by the device 15 sensitiveto temperature changes occurring in the live steam pipe 5 as follows: 15represents a pressure responsive device or servo-motor similar toelements 11 and 13, which by their action,,as previously described,control respectively throttle valves 3 and 13. Device 15, however isconnected to a fluid thermostat 17, containing a readily expansiblefluid, such as for instance ammonia, thermostat 17 being in turnconnected to pipe equally well'be directly connected tov the 1 steamsupply-16 and thus'control the furnace 10 in dependence from the steampressure prevailing inthe pipe line 15 insteadof through the varyingtemperature of' the steam. This particular modification of the controlwould not change anything in the arrangement shown, except that theelement 15 responds directly to the steam pressure vari ation instead ofindirectly thru the pressure of a thermostatic fluid.

The arrangement operates in the following manner: If for instance loadvariations occur in the consumer 6, 7, such that for instance the powerrequirement increases, the prime mover 6 will require more steam, Thisproduces in service pipe a decrease in pressure, however small it maybe. This pressure dev crease is communicated by pipe line 12 to thepressure responsive servo-motor 11-, which reacts thru the bending ofits diaphragm upon throttle 3, opening same further, so that moresteam'is supplied to the superheater. This decreases the steam pressurein steam generator 2 and accordingly pressure responsive servo-motor 13which is connected tq the output side of generator Qand which controlsthe feed-pump throttle 13 now comes into action. It opens throttle valve13 further,

thereby increasing the feed-water supply to generator 2. By thisincreased supply of feed water, the drop in pressure in service pipe 5,caused by the increased power consumption is compensated thru theincrease in generated steam. Since, however, thru this readjustment tonew operating conditions first an increased quantity of liquid operatingfluid must be heated by the heretofore prevailing quantity of fuelsupplied before the condition was changed, the increased quantity ofoperating fluid would not be heated to the temperature required. Inother words, the operating fluid would now be cooler.

This drop in temperature, however slight,

acts immediately upon thermostat 1-7, which in the manner describedbefore acts thru device 15 upon-throttle '18, which in turn controlsfuel supply pump 20 and thereby increases the fuel supply to the amountrequire by the new operating conditions. This fuel control by thethermostat has two effects. As soon as the pressure in service pipe 5assumes its normal value-and as soon as also the steam temperature isrestored to its normal value,

. the eifect is obtained that the critical temperature is restored insteam generator 2 an that at the same time the steam temperature in theservice pipe is restored to a value above the saturation temperature. Inthe control illustrated and described hereinabove thus three elementsindividually responsive to three varying conditions of the plant actsubstantially simultaneously in such manner that the pressure of theoperating fluid in the steam generator remains substantially at alltimes above critical valueeven at load variations, that further thetemperature of the aseaiso 3 tor, means for supplying: a liquidoperating medium to said generator, means for superheating the steamgenerated, said superheating means being supplied With steam from thegenerator, means for supplying heat to said generating and superheatingmeans, a service pipe connected to the outlet of the superheater forsupplying superheated steam at suitable pressure to the consumers, at

a different operating condition of the plant when the steam demandvaries, one control device being connected for its own control to theoutlet of the steam generator and between the generator "and thesuperheater,

means controlled by the last mentioned con-v trol device for maintainingthe pressure of the steamgenerated constant, the other control deviceincluding means for throttling the steam to service pressure, and formain-.

taining the throttle steam pressure constant at varying loads, saidother control device being responsive to pressure variations at thesuperheater outlet, and a third device responsive to temperatureconditions so of the steam, and means controlled by said third devicefor maintaining the temperature of the throttled steam constant.

2. In a steam generating system for variable outputs in combination asteam generator consisting of tubular heat transmitting elements ofconsiderable length and internal resistance, means for supplying aliquid operatmg medium to said generator, means for superheating thegenerated steam, means for supplyingheat to said generating and dsuperheating means, a service pipe connected to the superheater forsupplying superheated steam at suitable pressure to the consumers,

a plurality of control devices each respon- 1U sive to a differentoperating condition of the plant when the steam demand varies, one ofsaid devices being responsive to presd sure variations at the generatoroutlet, and

one to" temperature variations of the steam 11.

in the service pipe, means controlled by said pressureresponsive devicefor maintaining the pressure of the steam constant in the steamgenerating system irrespective of varying conditions existing in partsof the system Ill beyond the generating system, and means controlledby'the temperature responsive device for maintainingthetemperature ofthe steam in the service pipe constant.

3. In a steam generating system for vari- I.

able outputs in combination a steam genera-. tor consisting of tubularheat transmitting elements of considerable'length and internalresistance, means for supplying a liquid operating medium to saidgenerator, means for ll superheating the steam generated, means forsupplying heat to saidgenerating and superheating means, a service pipeconnected to the superheater for supplying steamat variable pressure tothe consumers, a

least two control devices, each responsive to 4 of control devices eachresponsive to a different operating condition of the plant when thesteam demand varies, one of said devices being responsive to pressurevariations at the generator outlet, and one to temperature variations ofthe steam in the service pipe, means controlled by said pressureresponsive device for maintaining the pressure of the steam constant inthe steam generating system and means controlled by the temperatureresponsive device for maintaining constant the temperature of the steamin the service pipe,'and a pressure controlled throttle element betweenthe generating and the superheating part of the system.

In testimony whereof I afiix my signature.

WALDEMAR STENDER.

